Development of an Escherichia coli-Lactobacillus casei shuttle vector for heterologous protein expression in Lactobacillus casei

Construction of a Novel Shuttle Vector for Tetragenococcus species based on a Cryptic Plasmid from Tetragenococcus halophilus

A cryptic plasmid (pTH32) was characterized from Tetragenococcus halophilus 32, an isolate from jeotgal, Korean traditional fermented seafood. pTH32 is 3,198 bp in size with G+C content of 35.84%, and contains 4 open reading frames (ORFs). orf1 and orf2 are 456 bp and 273 bp in size, respectively, and their translation products showed 65.16% and 69.35% similarities with RepB family plasmid replication initiators, respectively, suggesting the rolling-circle replication (RCR) mode of pTH32. orf3 and orf4 encodes putative hypothetical protein of 186 and 76 amino acids, respectively. A novel Tetragenococcus-Escherichia coli shuttle vector, pMJ32E (7.3 kb, Em^r), was constructed by ligation of pTH32 with pBluescript II KS(+) and an erythromycin resistance gene (ErmC). pMJ32E successfully replicated in Enterococcus faecalis 29212 and T. halophilus 31 but not in other LAB species. A pepA gene, encoding aminopeptidase A (PepA) from T. halophilus CY54, was successfully expressed in T. halophilus 31 using pMJ32E. The transformant (TF) showed higher PepA activity (49.8 U/mg protein) than T. halophilus 31 cell (control). When T. halophilus 31 TF was subculturd in MRS broth without antibiotic at 48 h intervals, 53.8% of cells retained pMJ32E after 96 h, and only 2.4% of cells retained pMJ32E after 14 days, supporting the RCR mode of pTH32. pMJ32E could be useful for the genetic engineering of Tetragenococcus and Enterococcus species.

The construction of recombinant Lactobacillus casei expressing hemagglutinin-neuraminidase protein and its immune response in chickens

Newcastle disease virus (NDV) is one of the most important diseases in poultry. The present study generated recombinant surface-displayed Lactobacillus casei (L. casei) expressing the hemagglutinin-neuraminidase (HN) of NDV (Lc-pPG-HN) and a live pPG vector (Lc-pPG) and evaluated their immunogenicity. A 1670 bp HN gene fragment was successfully amplified and cloned into a prokaryotic protein expression system. Protein expression in the resulting recombinant Lc-pPG-HN (surface displayed) strain was verified using Western blotting and indirect immunofluorescence. A single band was observed on the Western blots, and the molecular weight of the corresponding protein was 63 kDa. A fluorescent signal for Lc-pPG-HN was observed using fluorescence microscopy. A total of 270 healthy chicks were divided into three treatment groups. Five replicates were used for each treatment, while six chicks were used per replicate. The following three treatment groups were used: physiological saline group (Control), Lc-pPG group and recombinant vaccine group (Lc-pPG-HN). The primary immunization and booster immunization of the chicks were performed via oral administration on 1 and 10 days old. Tissue and blood samples were collected from chickens that received oral recombinant L. casei strains on 1, 7, 14 and 21 days post-immunization for immune-related index analyses. Chickens orally immunized with Lc-pPG-HN showed significantly increased body weights and immune organ indices. Oral immunization with Lc-pPG-HN also enhanced the concentrations of serum interleukin-2 (IL-2), interferon-γ (IFN-γ), intestinal lavage fluid secretory immunoglobulin A (SIgA) and histomorphological development of the small intestine. Our results also indicated that recombinant L. casei significantly increased Lactobacillus and Bifidobacterium colonization and decreased the relative abundance of Escherichia coli (E. coli) in the chicken caecum. Similar enhancement effects from hemagglutination inhibition were also observed in the antibody titers. Oral administration of Lc-pPG-HN effectively protected against NDV and alleviated the symptoms of the NDV challenge. In summary, recombinant L. casei had positive impacts on the performance, immunological function, gut development, and microbiota of growing chicks and may be a potential therapeutic candidate against NDV.

Detection and characterization of a theta-replicating plasmid pLP60 from Lactobacillus plantarum PC518 by inverse PCR

Plasmid DNA of Lactobacillus plantarum PC518 was isolated by an improved method which contained a washing step for removing lysozyme. Three plasmid DNA libraries were constructed. A pair of outward primers was designed at both ends of the novel plasmid fragment obtained from plasmid DNA libraries, and the remainder of the circle plasmid was amplified by inverse PCR (iPCR). The whole sequence of plasmid was analyzed by the basic local alignment search tool, Tandem Repeats Finder, DNAMAN V6.0, DNASTAR and MEGA X software. The copy number was measured using quantitative real-time PCR. Plasmid extract showed 7 bands on agarose gel, indicating that L. plantarum PC518 contains multiple plasmids. The complete sequence of plasmid pLP60 was obtained by plasmid DNA libraries and iPCR. pLP60 is 6006 bp in length with a G + C content of 41.19 %, which encodes 8 open reading frames (ORFs). The ori site like theta-type could be located upstream of repB, which contains a short tandem repeats (sTR) and a long tandem repeats (lTR). RepB of pLP60 only had low similarity with Rep protein of known theta-type plasmids, but phylogenetic tree analysis showed that plasmids whose Rep proteins are similar to pLP60 have lTR at ori, and the conservativeness of lTR is consistent with similarity of Rep proteins, suggesting that RepB of pLP60 is a theta-replicating protein. So pLP60 was classified as class A of theta replication. The copy number of pLP60 was measured as 5 copies per cell by qPCR.

Broad range shuttle vector construction and promoter evaluation for the use of Lactobacillus plantarum WCFS1 as a microbial engineering platform

As the field of synthetic biology grows, efforts to deploy complex genetic circuits in nonlaboratory strains of bacteria will continue to be a focus of research laboratories. Members of the Lactobacillus genus are good targets for synthetic biology research as several species are already used in many foods and as probiotics. Additionally, Lactobacilli offer a relatively safe vehicle for microbiological treatment of various health issues considering these commensals are often minor constituents of the gut microbial community and maintain allochthonous behavior. In order to generate a foundation for engineering, we developed a shuttle vector for subcloning in Escherichia coli and used it to characterize the transcriptional and translational activities of a number of promoters native to Lactobacillus plantarum WCFS1. Additionally, we demonstrated the use of this vector system in multiple Lactobacillus species, and provided examples of non-native promoter recognition by both L. plantarum and E. coli strains that might allow a shortcut assessment of circuit outputs. A variety of promoter activities were observed covering a range of protein expression levels peaking at various times throughout growth, and subsequent directed mutations were demonstrated and suggested to further increase the degree of output tuning. We believe these data show the potential for L. plantarum WCFS1 to be used as a nontraditional synthetic biology chassis and provide evidence that our system can be transitioned to other probiotic Lactobacillus species as well.

Survey on Heavy Metals Contamination and Health Risk Assessment in Commercially Valuable Asian Swamp Eel, Monopterus albus from Kelantan, Malaysia

This work investigates the metals concentration in the tissues of Asian swamp eel, Monopterus albus. Five selected tissues, including liver, gill, bone, skin, and muscle were examined for the concentration of Zn, Cu, Cd, Pb, and Ni. The concentrations of Cd and Pb were found high in the muscle tissues of the eels. Additionally, high amounts of Zn and Cu metals were observed in the liver, whereas the Cd, Pb, and Ni metals were highly detected in gill. The accumulation of Zn, Cu, Cd, Pb, and Ni in both skin and bone of the eel seems to vary between seasons. Low levels of Zn, Cu, and Ni were identified in the muscle tissues of the eels. This study revealed that the concentration of Cd and Pb in the muscle tissues of Asian swamp eels exceeded the permissible limits by the US EPA, suggesting the consumption of the muscle may be hazardous and can severely affect one’s health.

Lactobacillus Mucosal Vaccine Vectors: Immune Responses against Bacterial and Viral Antigens

Lactic acid bacteria (LAB) have been utilized since the 1990s for therapeutic heterologous gene expression. The ability of LAB to elicit an immune response against expressed foreign antigens has led to their exploration as potential mucosal vaccine candidates. LAB vaccine vectors offer many attractive advantages: simple, noninvasive administration (usually oral or intranasal), the acceptance and stability of genetic modifications, relatively low cost, and the highest level of safety possible. Experimentation using LAB of the genus Lactobacillus has become popular in recent years due to their ability to elicit strong systemic and mucosal immune responses. This article reviews Lactobacillus vaccine constructs, including Lactobacillus species, antigen expression, model organisms, and in vivo immune responses, with a primary focus on viral and bacterial antigens.

Gene editing and genetic engineering approaches for advanced probiotics: A review

The applications of probiotics are significant and thus resulted in need of genome analysis of probiotic strains. Various omics methods and systems biology approaches enables us to understand and optimize the metabolic processes. These techniques have increased the researcher's attention towards gut microbiome and provided a new source for the revelation of uncharacterized biosynthetic pathways which enables novel metabolic engineering approaches. In recent years, the broad and quantitative analysis of modified strains relies on systems biology tools such as in silico design which are commonly used methods for improving strain performance. The genetic manipulation of probiotic microorganisms is crucial for defining their role in intestinal microbiota and exploring their beneficial properties. This review describes an overview of gene editing and systems biology approaches, highlighting the advent of omics methods which allows the study of new routes for studying probiotic bacteria. We have also summarized gene editing tools like TALEN, ZFNs and CRISPR-Cas that edits or cleave the specific target DNA. Furthermore, in this review an overview of proposed design of advanced customized probiotic is also hypothesized to improvise the probiotics.